typescript: How to define type as any part of enum?

Question

I'm trying to create a translation module using typescript.

I want to define the languages as an enum parameter to create-text function, as like:


export enum Language {
    He = "he",
    En = "en",
}
const { createI18n, createI18nText } = createTextFunctions(Language);
const firstExample = createI18nText({
    he: {
        firstText: "שלום",
        sc: {
            hello: "שלום שוב"
        }
    },
    en: {
        firstText: "hello",
        sc: {
            hello: "hello again"
        }
    }
})
export const i18n = createI18n({
    welcome: firstExample,

})

But my problem is that because the languages are are passed as params to a typescript function and the function infers the types, typescript is not alarming anything. I can create text with non-existing language and it will pass it,like createI18nText({ ar:{ hi : "hi" }}).

My text functions are these:

export type Languages = { [key: string]: string };
export const createTextFunctions = (languages: LanguagesD) => {

    type I18nText<T extends object> = {
        [k in keyof typeof languages]: T;
    }

    const createI18n = <T extends { [key: string]: I18nText<any>; }>(i18n: T) => {
        return i18n;
    };

    const createI18nText = <T extends object>(text: I18nText<T>) => {
        return text;
    }

    return {
        createI18n,
        createI18nText
    }
}

So the code is running and doing whatever it needs to do, but I'm losing type control.

I do prefer to have my enum values lower-cased, so its an issue too. If this is the solution so I'll take it, but if there is any way to pass an enum-param and to run by its values it would be great.

Does this work for you to limit the language names to what's passed in? If not, please elaborate on what's missing. Otherwise I can write up an answer when I get a chance. — jcalz
– jcalz, Commented Jul 8, 2021 at 15:08

Baboo · Accepted Answer · 2021-07-08 15:45:52Z

1

You can make createTextFunctions use a generic. You will be able to customise the keys as you want when you create the text function :

// *L* must be a union of strings.
const createTextFunctions = <L extends string>() => {

    type I18nText<T extends object> = Record<L, T>;
    type I18n = Record<string, I18nText<any>>;

    const createI18n = <T extends I18n>(i18n: T): T => {
        return i18n;
    };

    const createI18nText = <T extends object>(text: I18nText<T>): I18nText<T> => {
        return text;
    }

    return {
        createI18n,
        createI18nText
    }
}

Then specify the Language as a union of strings:

type Language = "en" | "he";

And create/use the text functions:

const { createI18n, createI18nText } = createTextFunctions<Language>();

const firstExample = createI18nText({
  he: {
    firstText: "שלום",
    sc: {
      hello: "שלום שוב"
    }
  },
  // If the key *en* is missing, typescript will complain.
  en: {
    firstText: "hello",
    sc: {
      hello: "hello again"
    }
  },
  // If we add the key *us*, typescript will complain.
})

export const i18n = createI18n({
  welcome: firstExample,
})

IMO union types are more comfortable to use than enums.

answered Jul 8, 2021 at 15:45

Baboo

4,3184 gold badges24 silver badges41 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Reut Schremer Over a year ago

Thank you! It works, but I still prefer enum. @jcalz comment worked as well. Thanks for your effort!

Baboo Over a year ago

Don't forget to mark the question as answered then ;)

Collectives™ on Stack Overflow

typescript: How to define type as any part of enum?

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related